Question
Question: Green (Y) is dominant over yellow (y) in peas, and smooth allele (W) is dominant over wrinkled (w). ...
Green (Y) is dominant over yellow (y) in peas, and smooth allele (W) is dominant over wrinkled (w). Which of the following crosses produces green and smooth peas?
A) yyWw × yyWw
B) Yyww × YYWW
C) yyWW×yyWW
D) Yyww × yyww
Solution
Dihybrid cross is defined as a cross between two different genes. One of the genes is considered as dominant while the other one is recessive. Here, Y is dominant over y and W is dominant over w.
Complete answer:
Option A-
| Male/Female | yW | yw | yW | yw |
|---|---|---|---|---|
| yW | yyWW | yyWw | yyWw | yyww |
| yw | yyWw | yyww | yyWw | yyww |
| yW | yyWW | yyWw | yyWW | yyWw |
| yw | yyWw | yyww | yyWw | yyww |
yyWw- yellow smooth
yyWW- yellow smooth
yyww- yellow wrinkled
Option B – this cross is between green- wrinkled seed and green- smooth pea seed.
YyWw- green wrinkled
YYWW- green smooth
YYWw- green smooth
YYWw- green smooth
| Male/♀️ | Yw | yw | YW | YW |
|---|---|---|---|---|
| Yw | yyww | Yyww | YYWw | YYWw |
| yw | yyww | yyww | YyWw | YyWw |
| YW | YYWw | YyWw | YYWW | YYWW |
| YW | YYWw | YyWw | YYWW | YYWW |
So, the cross shows that the result which is obtained is green and smooth peas. He first worked to obtain a monohybrid cross which has genotypic ratio 3:1 and the phenotypic ratio is 1:2:1. After receiving the successful result with his experiment, he went further to cross two different genes together with the genotypic ratio very long and phenotypic ratio 9:3:3:1.
Option C
yyWW- yellow smooth
| Male/Female | yW | yW | yW | yW |
|---|---|---|---|---|
| yW | yyWW | yyWW | yyWW | yyWW |
| yW | yyWW | yyWW | yyWW | yyWW |
| yW | yyWW | yyWW | yyWW | yyWW |
| yW | yyWW | yyWW | yyWW | yyWW |
Option D-
Yyww- green wrinkled
yyww- yellow wrinkled
| Male/Female | Yw | yw | yw | yw |
|---|---|---|---|---|
| Yw | YYww | Yyww | Yyww | Yyww |
| yw | Yyww | yyww | yyww | yyww |
| yw | Yyww | yyww | yyww | yyww |
| yw | Yyww | yyww | yyww | yyww |
Note:
The three laws of inheritance are-
1. Law of dominance- One gene is dominant over the recessive gene.
2. Law of segregation – Alleles do not show any blending and both the characters are found as such in the second generation.
3. Law of independent assortment- It says when two pairs of traits are taken together, segregation of the characters is independent of the other pair of characters.